| RH vacuum refining is a complicated metallurgical process, which involves gas-liquid two-phase flow, heat and mass transfer and chemical reactions. The circulation degassing process is achieved through the bubble-driven liquid steel, and it is have an important impact on the vacuum refining efficiency that the Ar blowing conditions and the flow behavior of the bubbles in liquid steel. In the actual production process, it is difficult to measure accurately and research quantitatively on specific influence of the operation parameters and structure on the circulation refining efficiency. Then, an approach of physical simulation combined with numerical simulation has been a primary means to study the RH vacuum refining process and develop RH new technology, the new device model to improve the refining efficiency.In this paper, the water model simulation and computational fluid dynamics (CFD) numerical simulation method are used to link the microscopic behavior of bubble coalescence and breakage to the macroscopic behavior of bubble-driven efficiency. Considering the coordinated effect of the Ar blowing angle and Ar blowing flow rate on the circulation flow efficiency, the multiphase flow, mixing characteristics and bubble driven efficiency of RH refining process have been made a deep study. In addition, two new types of bottom blowing vacuum refining devices and a new side-bottom blowing vacuum refining device based on the traditional RH vacuum refining equipment have been put forward.The physical and numerical simulations are carried out, the main research works are as follows:(1) Taking an 180 t RH vacuum refining equipment in a steel plant as prototype, a RH vacuum degassing water simulation system with geometric similarity ratio of 1:5 was designed. The three-level orthogonal experiment with the influence of two factors such as injection angle and gas blowing flow rate were studied in water model experiments, which revealed thorough understanding of the circulating flow conditions in RH vacuum refining process, studying on the effect degree of the Ar blowing flow rate and Ar blowing angle on circulation flow rate.This study can provide further guidelines for setting appropriate Ar blowing parameters so as to improve the overall refining performance.(2) The three-dimensional mathematical model of gas-liquid two phase flow was established in RH vacuum refining process, the multiphase circulation flow behavior and the mixing characteristics of up-leg, vacuum chamber,down-leg and ladle have been obtained using CFD numerical method. Then, the effect of Ar blowing nozzle distribution and row spacing on the circulation flow rate under the same vacuum degree was discussed.After obtaining the steady flow field, the mixing characteristics of RH refining process were simulated by the tracer concentration diffusion model. The tracer concentration-time curve is agreed well with the physical simulation results.(3) To further explore the circulation flow law of RH vacuum refining process, a CFD-Population Balance Model (CFD-PBM) was established based on the steady flow field. It introduced the bubble coalescence and breakage behaviors into the CFD solution framework, considering the effect of the bubble coalescence and breakage on circulation flow behavior, and made a quantitative description on the bubble size distribution and gas phase structure. The bubble behavior and its evolution law have been obtained, which further understood the bubble internal driving force of RH vacuum refining process and sought a control method for circulation flow rate and the flow field structure of RH vacuum refining process, and which provides a theoretical basis for maximizing the refining efficiency.(4) The design point was obtained using the Design of Experiment (DOE) method by the DesignXplorer optimization design module in ANSYS Workbench Environment (AWE). The maximum of average flow rate at the outlet of down-leg of the RH vacuum refining equipment was chose to be the optimal goal, the collaborative effect of Ar blowing angle and Ar blowing flow rate on the circulation flow rate was numerically investigated,and acquired the design parameter combination with Monte Carlo sampling technique, and calculated the response of optimization objective on each sample point, and the response surface cloud pictures and response curves in design space with quadratic interpolation function were structured, searched for the extreme values of target function, and achieved the coordinated optimization design of argon blowing parameters in RH vacuum refining equipment.(5) Two new types of bottom blowing vacuum refining devices and a new side-bottom blowing vacuum refining device based on the traditional RH vacuum refining equipment have been put forward.The gas-liquid two phase circulation flow of the three kinds of new type of vacuum refining equipments are simulated using the physical simulation and numerical simulation. The characteristics of circulation flow and mixing time were analyzed, which made an important attempt to seek of the maximize efficiency by bubble-driven and the new structure of RH vacuum refining equipment. |
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